1. Field of the Invention
This invention relates to an apparatus for conveying and mounting electronic parts, wherein the electronic parts are conveyed to the vicinity of a printed board and mounted thereonto.
2. Related Art Statement
An automatic mounting apparatus for mounting electronic parts, such as semiconductor chips enclosed in a package, onto a printed board is called a chip mounter, and the mounting apparatus comprises: conveyors for conveying a printed board; a part supply device for conveying the electronic parts to be mounted onto the printed board; and a mounter, i.e., a mounting machine having a mounting head for mounting the electronic parts onto the printed board. In the part supply device, a various type of means are previously provided adjacent to the conveyors, said means supplying the electronic parts in association with their forms, dimensions and packing styles, and said means also mounting or removing the electronic parts according to the need.
As another type of part supply device for conveying small-sized electronic parts, such a type of device is known that the electronic parts which are previously packed for supplying purpose are loaded into the device with keeping the packing style (as the general packing style used in the device, the electronic parts are pasted or sealed by a tape on paper or synthetic resin tapes, or the electronic parts are inserted into synthetic resin tubes). In this device, the electronic parts are successively taken out of the package at the loaded position and are conveyed to a predetermined mounting position for delivering them to the mounting head of the mounter, and the parts are held at the mounting position. The held electronic parts at the predetermined mounting position are taken up by the mounting head of the mounter by a preferable method, such as vacuum sucking, and they are conveyed to a printed board and mounted thereon.
The packing styles of the small-sized electronic parts are generally described as above. However, large-sized parts such as QFP (Quad Flat Package) are often contained in a tray and conveyed to a predetermined position apart from the above-described method. Furthermore, it is difficult to convey and supply some kind of electronic parts, such as so-called bare chips, without using a tray in view of the nature or the manufacturing process of the parts. Combined with the improvements in the mounting technique due to the image processing in recent years in particular, the method of conveying and supplying the parts by use of trays has enhanced its importance.
The inventor of the present invention has examined techniques of conveying the electronic parts by use of trays. The following is the techniques examined by the inventor, and the outlines thereof will be described as below.
That is, there are the following three methods as ones for conveying and supplying the parts, which have heretofore been thought of. A first method has such arrangements that, for example, as disclosed in the Japanese Patent Laid-Open No. 5-235587 (corresponding to the U.S. Pat. No. 5,295,294), one or a plurality of trays are provided at the outside of the movable area of the mounting head of the mounter, and that such a means (so-called "pick and place" means) is provided for successively taking out a predetermined electronic parts from a tray and placing those parts on a transferring means (such as a shuttle for transferring the parts from a position close to the tray into movable area of the mounting head). In this case, the electronic parts transferred to the mounting position are mounted onto the printed board by the mounting head of the mounter.
In this method, there are such advantages that the number of trays is not limited and that supply and exchange of the trays can be made even during the operation of the mounter. On the other hand, there are such disadvantages in the method that it is necessary to provide mechanisms such as a means for controlling "pick and place", the shuttle means, and a means for selecting desirable electronic parts from a plurality of trays, in which the mechanisms become complicated, the cost of the whole apparatus is increased and a considerable space is required, and so forth. Therefore, in the case where many types of the electronic parts (a number of trays) are not particularly required, this method is often regarded as being not most suitable one. Furthermore, there is also such a disadvantage in that method that the mounting speed is generally limited in accordance with the conveying capacity (speed) of the shuttle when the same parts are continuously mounted.
The following method is considered as a second method in which a tray is provided in the movable area of the mounting head of the mounter, keeping the tray away from a conveying region of the printed board, and a predetermined electronic parts are directly taken up by a preferable means, such as a mounting head, and then mounted onto the printed board.
Although it is necessary to provide on the side of the mounter a controlling element for successively taking up the electronic parts in a lattice arrangement in this method, the method has a very simple construction, so that the method is often used in the case where it is not necessary to simultaneously supply a multiple type of the electronic parts. However, in the movable area of the mounting head in the mounter, the dimensions of the conveying direction of the printed board are generally determined by the width of the arrangement of the part supply device. Further, the dimensions in a direction perpendicularly intersecting the conveying direction of the printed board (generally, in the axial direction) are designed in accordance with the largest dimensions of the printed board mountable onto the mounter (generally, the largest conveying width), so that, normally, no space is remained in the mounter other than the above in view of the movable area of the mounting head. Accordingly, when the electronic parts are mounted onto the printed board having the largest dimensions, this method cannot be used because there is no space for providing the tray.
In order to apply this method effectively, such a condition is required that the width of the printed board with the electronic parts mounted thereon is satisfactorily small with respect to the largest width of the mounter. As the width of the printed board becomes larger, the number and the dimensions of the trays to be provided are limited. Furthermore, with this method, it is inevitably impossible to perform works for supplying or exchanging the trays or the electronic parts during the operation of the mounter.
As a third method, there is a method in which a plurality of trays are normally loaded in the vicinity of the movable area of the mounting head provided in the mounter. In this case, one tray is selected out of a plurality of trays, transferred into the movable area of the mounting head, and positioned. Similarly to the second method, the electronic parts are directly mounted onto the printed board in this method without using a transferring means like a shuttle.
This method is intended to obviate the problem of the difficulties in supplying the electronic parts and exchanging their types during the operation, said problem being the weak point of the second method. However, inconsistence between the dimensions of the printed board and the dimensions of the tray cannot be obviated because a scope within which the tray transferred from the loaded position is transferred to a predetermined mounting position is same as one in the second method. Accordingly, similarly to the second method, this method is effective under the specific manufacturing situation, however, this method greatly lacks the possibility of accommodation for the situation which is not easily specified, i.e., a future production.
As described above, the above three methods are thought of at present. However, the respective methods has advantages and disadvantages, and it is difficult to select the apparatus for supplying and conveying the electronic parts, which can make the capacity of the mounter to be achieved to the utmost.